Daverehm
FWIW, I went solo at 22.5 hours aged 48. I too was getting frustrated, not with the instructor but with myself. I found the whole thing to be far more difficult than I anticipated. I guess I saw it as a failure on my part, especially seeing the young guns going off at 12 or 15 hours.
I finally passed my skill test at 75 hours, the whole process taking five months elapsed. On a positive note I did get the night qualification in 5 hours 5 minutes. But the IR(R) is really a struggle for me, I am already at 15 hours, and I'd not be surprised if I need another 10 or 15 to get to test standard.
The other thing I found was that unlike passing a driving test, once you've got your PPL, there's a whole lot more to learn about before being confident enough to do that £200 escargot and garlic trip to France.
I have just had to accept that the old grey matter ain't as malleable as it once was. That's life I'm afraid.